Connecting two dial-up modems using a VoIP ATA
Semi-related: I remember needing to send a fax to some institution. I had a multi-function device that's a printer, scanner, copier and fax in one on my WiFi network, and I didn't want to waste paper so I'd just use Windows' Print to Fax feature to send the fax.
I remember contemplating how many encapsulations the document went through: it's supposedly a paper document, but it's all just digital, it went over WiFi to the device, the device dialed the number, and since I was using a cable modem, it did Fax over IP, and at the receiving end it probably never got printed on paper either, being received by a machine that converted it to a JPG/PDF...
If you are going to use the SPA series from Cisco/Linksys/Sipura, just be careful to not expose them to the internet or use them on sensitive networks - there’s a really gnarly remote firmware flashing bug in them.
https://www.fullspectrum.dev/cisco-spa112-forever-day-cve-20...
Not to hijack the thread, but we are talking about weird things you can do with ATAs here: anyone know of an ATA with a cell modem? I’m responsible for a municipal septic pump with an autodialer in the control station for alarms. It would be nice to get a phone call from it if it fails.
I built a mobile app to read data from blood glucose meters.
It used a magic cable that talked to the meters using RS-232 and converted the data into audio, plugging into the audio jack on the phone.
So, basically, it was a modem. The cable just had a little bump on it that did everything you used to do with a huge device.
Another option I've used in the past is a Cisco voice gateway (like the VG204) or an FXS card in a random old router configured to be able to just route calls between analog ports. The nice way doing it through the VG is it'll pass analog straight through each other without any codec mangling.
I have a VG224 set up like this (local extensions 1001-1024), including a hunt group on x31337 that dials 8 modems I've got connected via a Shiva LanRover.
The bonus with the VGs is they don't need to be networked - you can keep them fully isolated to POTS-only and just use a console cable to set up the config. Of course, if you network them, then you can do Even More Fun Things...
Once upon a time I owned a little black box that would simulate enough of a phone system that you could plug two computers' modems into it and computer A would get a dial tone and computer B would get a ring.
It was great for developing and testing dialup-based software without having to tie up real phone lines.
Or you can emulate the POTS network: two wires with 24-48VDC present.
I remember when VoIP ATAs first came out that one of the cardinal rules was not to use them with dial-up modems, since the codecs used didn't do well with the encoding schemes used a 33.6kbps and 56kbps.
What has changed since then that makes this work now? (Are networks fast enough that ATA just send PCM now?)
ATA: Analog Telephone Adapter
Ah, some good ol' IPoIP
> Calling Over The Internet
I suspect this would not work all that well. Modems were designed in an age when the phone system was circuit-switched, so the protocols involved expect zero "packet" loss and zero jitter. Granted, later modem encoding standards became more tolerant (as the phone system evolved and became less "clean"), but I suspect most home internet links are going to have too much packet loss and jitter for this to work all that well. But it'd probably still be fun to play with.
I never got anywhere with this, but as a kid, I was annoyed I couldn't easily create a two-computer network with modems and a cable.
I remember having to support this device as a VoIP Support engineer. At least the SPA122 works fine if all you need it for is DAC/ADC.
Cisco's SPA 232D, which they frankensteined to support wireless handsets for some reason, is possibly the worse single piece of consumer hardware I have ever had the displeasure in troubleshooting.
He got 33.6K doing this? Was it reliable? I did something similar to transfer files to & from a mainframe and ended throttling back to 2400 baud to get a solidly reliable connection. Not a big deal, the files were only hundreds or thousands of bytes.
Won't the VoIP codec break the modulation? I doubt the speeds would be stellar, anyway.
never thought I'd see gravis on HN lol